It is well known to collect dust particles and other particulate material in containers or the like for later disposal or use. The containers may be provided with an air filter system. The material may be supplied to the containers by means of a gaseous flow through a ducting. The dust may be explosive. In some situations, an ignition may occur in the container due to ignition sources transported to the container with the airflow or due to ignition sources inside the container. Such ignition may result in devastating effects both on personnel, buildings, and the equipment, since the ignition may cause an explosion with a pressure wave and a flame front which propagates along the ducting opposite to the normal airflow direction.
In order of preventing such pressure wave and flame front from travelling back along the ducting, it is well known to provide a back pressure flap valve arrangement in the ducting. The back pressure flap valve arrangement typically comprises a flap which is arranged to act as a check valve which may close off the ducting. During normal operation the flap is maintained in an open position by the dust or particle laden air stream flowing along the ducting. In the occasion of sudden pressure wave resulting from an upstream explosion, the flap is arranged to close the passage through the ducting by the pressure wave acting on the flap. To avoid any rebound of the flap it is known to use a locking mechanism. One such locking mechanism is known from e.g. DE 202009011668U1.
Regulations require solutions where the flap stays closed long enough to avoid flames from transmitting during an explosion event, see European Standard BS EN 16447:2014 with the title Explosion isolation flap valves. The standard stipulates that the parts making up the flap valve should be designed such that it can withstand the loads imposed by any explosion that can be expected in accordance with its intended use without losing its ability to perform its safety function.
The loads imposed by an explosion may be very high, whereby the flap and its locking mechanism must be designed to meet such loads. Still, the design must not interfere with the normal functionality of the ducting and the flap.